How can I make my dog less aggressive and more comfortable with strangers?

Well, my dog Smokey is a German Shepherd(According to the previous owner, he is part wolf as well), and on July 31st he'll be 2 years old. We got him from a friend who's dog(Wolf - German Shepherd hybrid) had puppies. We got Smokey when he was about 4 months old. About a week later we took him to Petsmart and he behaved normally, he wasn't scared or aggressive. People pet him and touched him but he didn't respond in any negative way. He was only aggressive to strangers' dogs. So after his vaccinations and such, we had him neutered. After getting neutered everything started to change. He started to feel more scared around people, especially men. After taking him to dog parks, he always growled and barked aggressively to other dogs. He was always more aggressive on a leash and when he had a muzzle. Whenever we took the leash and muzzle off, he would bark aggressively, threaten the person or dog(from a distance) and run away from them, staying as far as possible. When you get used to him, he's very loving, obedient, and playful. Smokey is only calm around dogs or people he is used to like family members. A friend of mine lived at my house for a week but after a day or two Smokey got used to her, and wasn't aggressive or scared anymore. We tried many things to control his behavior. We tried having a dog trainer see him, which didn't help so much. The dog trainer explained to us that he may have been traumatized at the kennels where he was neutered, and he is more aggressive on leashes because he can't escape from what is threatening him. We also tried aroma therapy which didn't work either. What can I do to help him be more outgoing with people and other dogs? I will not euthanize him, because he's a really important part of my life.|||It sounds like to me, that your dog is fearful. I can't say much more(since I'm not a dog trainer) other than I suggest checking out the dog whisperer. He is AMAZING. Hey, if anything you could always try getting him to come help you! :) I also suggest buying one of his books. They are great. Or watch the show. It's on National Geographic channel. His teachings could really help you! Hope this was helpful! (: check out his website below.|||learn to control the thing. watch the dog whisperer.